Seeking to help advertisers capture the attention of the sport’s millions of fans, the company has built a tool for its search product that places ads alongside football-related results. The ads will run before official N.F.L. video clips that will appear in a box at the top of the page, next to scores and news items.

Google’s N.F.L. offering is one of the many football-related marketing programs that websites and social networks have introduced to woo advertisers, who are clamoring for new ways to capitalize on live events — and the way that people flock to social media to talk about them. As advertisers increasingly look for ways to align themselves with football games beyond television commercials, the competition for ad dollars among digital players — including Facebook, Twitter and Snapchat — is heating up.

In addition to Google’s ad program, Facebook is shopping around marketing products that allow advertisers to target football fans and run campaigns around N.F.L. and college games. Twitter now offers several live-event tools for advertisers, including one for brands to sponsor clips related to the N.F.L. Snapchat, the fast-growing smartphone app, is working to secure a partnership with the league to push out weekly football-related video stories, with spots for ads. Even Vox Media is getting involved, creating a website for the technology company Lenovo centered on fantasy football.

“We’re entering a time when there are going to be a phenomenal number of opportunities for brands,” said Jill Sherman, senior vice president for social strategy at the digital agency DigitasLBi. “The opportunities that we’re seeing this year are really about wrapping brands more tightly around the real-time conversation.”

Brands and agency executives cite various reasons for wanting to advertise online during live events, including a rise in the number of people using their mobile devices while watching television. According to Nielsen, the television research firm, 88 percent of tablet owners and 86 percent of smartphone owners use their devices while watching TV.

Executives also said that the push into real-time digital advertising follows an increase in the number of so-called cord-cutters, those who have dropped their cable service but still want in on the live action. Advertising online can also be less expensive than buying commercial time on TV.

One brand making a big move into digital advertising is Bud Light, a behemoth when it comes to ad spending during the football season. The brand spent roughly $57 million on advertising during the N.F.L. regular season last year, according to Kantar Media.

Along with advertising on social networks like Twitter and Facebook, Bud Light has signed up for Google’s football program with the goal of reaching fans at relevant moments, said Lucas Herscovici, vice president for consumer connections at Anheuser-Busch InBev, which owns Bud Light.

When users search Google for information on a specific team, a relevant 15-second Bud Light ad could run before N.F.L. videos that turn up. A highlight video that appears for a New England Patriots fan, for instance, might feature an ad with Bud Light cans bearing the team’s logo.

These “pre-roll ads” will also run on the N.F.L.’s YouTube channel, introduced in January.

Bud Light’s digital strategy for the football season represents a broader shift in how brands think about their ad budget for live events. Advertisers say TV commercials are still highly desirable because they can reach more viewers than other kinds of ads. But that appeal has driven up the price of TV spots, often making it more cost-effective to buy digital ads around an event. (Leslie Moonves, chief executive of CBS, said in a recent earnings call that Super Bowl advertising was “already proving to be more lucrative than ever,” with 30 seconds of ad time going for $5 million.)

For Google and other companies, the ad program is a way to capitalize on the increased search activity during games.

“We see a ton of query volume happening in Google Search, particularly while events are happening live,” said Tim Katz, who leads sports partnerships for YouTube. “This is a great way for us, from an advertising perspective, to become part of the conversation.”

Social platforms like Facebook and Twitter said they saw this online activity as a way to attract a bigger portion of advertisers’ digital spending — particularly mobile spending, which the research firm eMarketer estimates will reach $30.5 billion in the United States this year. That figure would make up 52.4 percent of the projected total digital spending.

For the first time, Facebook is offering advertisers the ability to target N.F.L. and college football fans during the season using what it calls real-time clusters. These are segments of users who have indicated an interest in football by, for example, updating their statuses, liking a football-related post or posting football-related links. The company is also offering a product called accelerated-delivery technology, which allows brands to show their ads to a target audience during a limited time period to align with a live event like a football game or presidential debate.

Microsoft, which has used Facebook’s targeting tool in the past, will probably do so again this football season to advertise to specific audience segments, said Amy Stettler, a marketing executive at the company. The strategy, she added, has helped the company connect with more young consumers.

“We really find that Facebook is actually delivering reach as a priority,” she said. “That seems to be their strength right now.”

Lowe’s, the home-improvement retailer, plans to use Facebook’s targeting product during the season as well, with its ads heavily focused on Thursday night games — and aimed at sending customers to their stores over the weekend.

Twitter is pitching a new ad product this football season called “event targeting,” which lets brands identify big events across the globe, glean information about the potential audience based on data from previous years and create an ad campaign through a one-click process.

The company said presidential candidates including Rand Paul and Chris Christie used the product, which was introduced in July, around the first Republican presidential debate on Aug. 6. Snapchat is also trying to attract advertisers around football games. In addition to its hoped-for weekly N.F.L.-related video, the social platform is considering introducing sponsored geofilters — digital stickers that allow users to tag their location — for professional and college football stadiums.

So many real-time digital ad options, however, also bring the risk that brands’ messages will get lost in a cluttered landscape. Industry experts said it was important for brands to think carefully before advertising around live events to ensure that being part of the real-time conversation made sense.

“It’s authentic relevance that matters,” said Ameet Ranadive, senior director for revenue product at Twitter, which has a content planning team that works with advertisers on the voice and personality they project on the platform. “Sometimes, if a brand is trying and stretching to be part of an event, it comes across as not authentic.”